The invention relates to a method for designing a drilling plan for rock cavern excavation, the drilling plan defining in advance for a round to be drilled in a tunnel face at least the locations of drill holes in a predetermined coordinate system, and the method creating the drilling plan by means of a computer-assisted design program. The invention further relates to an arrangement for designing a drilling plan for excavating a rock cavern with a rock drilling apparatus comprising one or more drilling booms having a rock drilling unit attached to it and a control unit for controlling drilling, which arrangement comprises a computer for designing or modifying the drilling plan, whereby in the drilling plan at least locations of drill holes in a predetermined coordinate system has been defined in advance for a round to be drilled.
Tunnels, underground storage silos and other rock facilities are excavated in rounds. In a tunnel face, drill holes are drilled which are charged and blasted after drilling. One blast detaches from the rock an amount of rock material that equals that of one round. For excavating a rock cavern, a plan is made in advance and information is determined about the rock type, inter alia. In general, the orderer of the rock cavern also sets various quality requirements for the cavern to be excavated.
When face drilling is performed by a rock drilling apparatus provided with instrumentation, there is generally designed, as office work, a drilling plan for drilling a round, in which process attention is also paid to a charging plan provided for blasting the round. This drilling plan is supplied to the rock drilling apparatus for being used by means of its control computer. The drilling plan serves as a controlled instruction for drilling drill holes in the rock in such a manner that a desired round can be formed.
The successfulness of the drilling plan, drilling and charging is measured, inter alia, by pull-out per round, which refers to the ratio of an advance of the tunnel after the blast to the designed length in the drilling plan. To improve the pull-out from 88 to 95 percent, for instance, means significant cost savings in an excavation project. In practice, optimal pull-out is to be found out by changing the drilling plan, the parameters here including positioning, orientation and number of drill holes, blast cut, specific charge in different plan zones.
For designing a drilling plan there are developed design programs that assist the designer in composing the drilling plan. Designing a drilling plan is thus interactive action between the designer and the design program.
Production of drilling plans and continuous design, as well as review of plans during tunnel work, have been developed in various ways, for instance, in view of blasting techniques. Prior art is represented, for instance, by publication WO 2008/078001.
In practice, in round blasting it has been found that even though the hole locations and the size and amount of blasting charges are designed on the basis of the known facts as well as possible, the outcome of the blast does not, however, meet the planned design. Typically, when detached material is removed after the blast, it may be found that the remaining rock surface deviates significantly from the theoretical surface that should have been obtained after the blast. This may result from a plurality of different factors, such as fracturing properties or hardness of rock, or some other factor that cannot have been known in advance with a sufficient accuracy. As a consequence, however, the efficiency of excavation deteriorates and this, in turn, causes quite significant additional costs.